Not every industry has to worry so much about foreign materials or other contaminants entering their conveyor systems and falling into their product. But such concerns are critical in the food industry. And when that food is fresh produce, it becomes that much more important.
“It goes from the field to the table. You can’t cook it on the way, and you can’t sterilize it on the way,” says Eric Moulton, vice president of engineering at McEntire Produce. “So we have to be extremely careful with everything that we do to make sure that food safety is preserved across the supply chain from the time it’s in the field all the way to the time it gets to the table.”
Established in the late 1930s, McEntire Produce prides itself on state-of-the-art equipment and the highest levels of food safety. It has a history of innovating for food safety, having developed and launched a revolutionary wash system for fresh-cut processing in 2013. It was with this history in mind that McEntire Produce approached Graphite Metallizing in late 2020 to discuss its quality assurance efforts around the bearings in their conveyor systems.
Key points of concern
When McEntire Produce thinks about ensuring food quality for its customers, it’s important not only to keep the produce fresh and clean, but also completely free of foreign materials. Food products, such as lettuce and other greens, move through the processing plant on conveyor systems, and in some areas one conveyor necessarily operates above another. These spots are where McEntire Produce’s engineering team focused its attention—particularly on the bearings within those conveyors.
Bearings—a necessary part of any conveyor system—can cause problems on the foreign materials front. “They wear, and it’s difficult externally to tell how fast they’re wearing. And at some point, if you run a bearing for long enough, it will fall apart. And every bearing is the same inside—it’s got lots of small metal balls,” Moulton comments. “There’s just a huge inherent risk in using bearings if there are places where the bearings are over the product. So the biggest risk that we were concerned about was the bearings falling apart, and metal getting into the food. Secondary to that is the grease. We use food-grade grease, obviously, but that is still treated very seriously as a potential product contaminant.”
The production and maintenance teams monitor the bearings closely for any signs of bearing deterioration or grease egress, but McEntire Produce wanted to do more than just try to catch failures early. The engineering team had tested several different grease regimens and greaseless bearings, always looking for ways to mitigate what continued to be a risk. They tried the highest-end bearings from a few different manufacturers, but every one of them failed the test.
Everything in the plant is washed down every 24 hours, and every conveyor is thoroughly cleaned and sanitized with chemical foam and chlorinated water. The McEntire engineering team understands that heavy washdowns negatively impact traditional bearings, as water intrusion rapidly accelerates bearing degradation. “We don’t do pressure washing here, but we still see water intrusion into bearings and other mechanical components,” Moulton says. “We said we need something that’s going to last, and last a long time. We don’t want any risk of grease getting in the food. We don’t want the risk of early bearing failure because somebody didn’t grease it well enough or greased it too much and blew out the seals.”
After just weeks of testing the bearings at various places around the facility, Moulton and his team would take them off the conveyors and cut them open to see if there was water intrusion. “Every single bearing had water intrusion; all of them, even high-end IP69K washdown bearings,” he says. “They were all showing signs of rust and deterioration on the inside.”
At a loss as to what to try next, the engineering team instead tried backstop measures. “We tried to come up with other clever solutions, like putting little catch pans underneath every bearing to catch any stray grease or any ball bearings that fell out, but it just didn’t work well,” Moulton says. “And it’s a bad solution for us. We don’t want to have things like catch pans around because those are places for water to get trapped, and that creates the potential for bacteria growth.”
Graphalloy bearings provide the answer
Finally, Moulton learned about Graphite Metallizing’s Graphalloy bearings—which are self-lubricating, have no moving parts, are chemical- and temperature-resistant, and are essentially waterproof. After doing so many failed tests on what had been presented as the magic bullet from other manufacturers, he remained skeptical that Graphalloy bearings would be any different. But he made the call and got samples of the bearings.
Right away, Moulton saw the potential. “I thought, ‘Wow, this has real opportunity’,” he says. “They can not only run underwater continuously, but immersed in chemicals—continuously spinning under chemicals. If they can do that, surely they can handle a little bit of cold water.”
The McEntire maintenance team installed the first Graphalloy bearings on the conveyor systems in March 2021—at first on a conveyor that was not over food contact because they didn’t know what to expect. They checked the bearings every three weeks, then every six weeks, and then every few months, Moulton says. They’re still living up to every claim.
“We couldn’t have been happier. So we got a couple more and we put them over food contact surfaces,” Moulton says. One or two of those bearings were on a particularly difficult application—an inclined conveyor that typically has 400 lb of produce on it, running 16 hours a day and stopping and starting every 15 seconds. “We let them run for a couple weeks, and that was problem solved.”
There are a few key factors that make Graphalloy bearings particularly suited for McEntire Produce’s plant:
- No grease needed—Made of a graphite/metal alloy that is self-lubricating, Graphalloy works efficiently without external lubrication. This eliminates the risk of grease escaping from the bearing housing and reaching the product stream, and it saves maintenance time and money.
- Durability—Temperature- and chemical-resistant, Graphalloy bearings function reliably in cold, wet environments. They can withstand the cleaning chemicals and repeated heavy washdowns that take place at the plant daily.
- No risk from bearing failure—McEntire’s engineering team wanted to make sure that any new bearing product tried could be discovered through the metal detectors in case they failed. Not only is the Graphalloy bearing material detectable, but the bearings also don’t fall apart as they wear like traditional bearings.
There was a bit of a learning curve to understand how Graphalloy bearings wear differently than other bearings, Moulton notes. “The graphite doesn’t move, it sits. And if you’re pulling against it in one direction while you spin and spin and spin and spin, then you eventually wear away sort of an oval shape,” he explains. “The easy solution is you just take the bearings off and you spin them around 180 degrees after some wear period, and then you put them back on and wear them back the other way. Then, once a bearing gets too thin, you just replace it.”
McEntire now has almost 70 Graphalloy bearings in place everywhere that would be over a food contact surface or over product, Moulton says. “Every single bearing over a food contact surface in the whole plant has been replaced,” he says. “And then we have standard bearings everywhere else.”